Definition of a Triangle

Median of a Triangle, Definition, Theorem & Formula - Lesson

How to Find the Centroid of a Triangle (Formula, Definition, & Video)

The Triangle Plane Geometry Review at MATHalino

Triangle -- from Wolfram MathWorld

Princess Browne

Properties of Triangle - types & formulas [Video & Practice]

Triangles in Geometry (Definition, Shape, Types, Properties & Examples)

Geo 4.1 triangles

Properties of triangles - KS3 Maths - BBC Bitesize

Heron's Formula